FODMAPs can cause digestive discomfort in people who are hypersensitive to luminal distension, but they do not cause intestinal inflammation. In fact, FODMAPs help avert digestive discomfort because they produce beneficial alterations in the gut flora.[3][4][5][6]

FODMAPs, especially fructans, are present in small amounts in gluten-containing grains and have been identified as a possible cause of symptoms in people with non-celiac gluten sensitivity.[13][14][15][13][16][3] They are only minor sources of FODMAPs when eaten in the usual standard quantities in the daily diet.[13] As of 2019, reviews conclude that although FODMAPs present in wheat and related grains may play a role in non-celiac gluten sensitivity, they only explain certain gastrointestinal symptoms, such as bloating, but not the extra-digestive symptoms that people with non-celiac gluten sensitivity may develop, such as neurological disorders, fibromyalgia, psychological disturbances, and dermatitis.[3][17][13] The use of a low FODMAP diet without a previous medical evaluation could cause health risks because it can ameliorate and mask digestive symptoms of celiac disease, delaying or avoiding its correct diagnosis and therapy.[18]

Absorption

FODMAPs are poorly absorbed in the small intestine and subsequently fermented by the bacteria in the distal small and proximal large intestine. This is a normal phenomenon, common to everyone. The resultant production of gas potentially results in bloating and flatulence.[7]

Nevertheless, although FODMAP can cause certain digestive discomfort in some people, not only do they not cause intestinal inflammation, but they avoid it, because they produce beneficial alterations in the intestinal flora that contribute to maintain the good health of the colon.[4][5][6]

Fructose malabsorption and lactose intolerance may produce IBS symptoms through the same mechanism but, unlike with other FODMAPs, poor absorption of fructose is found in only a minority and, in certain populations, notably those of European descent, lactose intolerance is found in only a minority.[19] Many who benefit from a low FODMAP diet need not restrict fructose or lactose. It is possible to identify these two conditions with hydrogen and methanebreath testing and thus eliminate the necessity for dietary compliance if possible.[7]

Sources in the diet

The significance of sources of FODMAPs varies through differences in dietary groups such as geography, ethnicity and other factors.[7] Commonly used FODMAPs comprise the following:[20]

Other sources confirm the suitability of these and suggest some additional foods.[25]

Effectiveness and risks

A low-FODMAP diet might help to improve short-term digestive symptoms in adults with irritable bowel syndrome,[8][9][10][11] but its long-term follow-up can have negative effects because it causes a detrimental impact on the gut microbiota and metabolome.[2][9][11][12] It should only be used for short periods of time and under the advice of a specialist.[26] More studies are needed to evaluate its effectiveness in children with irritable bowel syndrome.[8]
There is only a little evidence of its effectiveness in treating functional symptoms in inflammatory bowel disease from small studies which are susceptible to bias.[27][28] More studies are needed to assess the true impact of this diet on health.[9][11]

In addition, the use of a low-FODMAP diet without medical advice can lead to serious health risks, including nutritional deficiencies and misdiagnosis, so it is advisable to conduct a complete medical evaluation before starting a low-FODMAP diet to ensure a correct diagnosis and that the appropriate therapy can be undertaken.[18]

Since the consumption of gluten is suppressed or reduced with a low-FODMAP diet, the improvement of the digestive symptoms with this diet may not be related to the withdrawal of the FODMAPs, but of gluten, indicating the presence of an unrecognized celiac disease, avoiding its diagnosis and correct treatment, with the consequent risk of several serious health complications, including various types of cancer.[18][29]

A low-FODMAP diet is highly restrictive in various groups of nutrients, can be impractical to follow in the long-term and may add an unnecessary financial burden.[28]

Over many years, there have been multiple observations that ingestion of certain short-chain carbohydrates, including lactose, fructose and sorbitol, fructans and galactooligosaccharides, can induce gastrointestinal discomfort similar to that of people with irritable bowel syndrome. These studies also showed that dietary restriction of short-chain carbohydrates was associated with symptoms improvement.[30]

These short-chain carbohydrates (lactose, fructose and sorbitol, fructans and GOS) behave similarly in the intestine. Firstly, being small molecules and either poorly absorbed or not absorbed at all, they drag water into the intestine via osmosis.[31] Secondly, these molecules are readily fermented by colonic bacteria, so upon malabsorption in the small intestine they enter the large intestine where they generate gases (hydrogen, carbon dioxide and methane).[7] The dual actions of these carbohydrates cause an expansion in volume of intestinal contents, which stretches the intestinal wall and stimulates nerves in the gut. It is this ‘stretching’ that triggers the sensations of pain and discomfort that are commonly experienced by IBS sufferers.[2]

The FODMAP concept was first published in 2005 as part of a hypothesis paper.[1] In this paper, it was proposed that a collective reduction in the dietary intake of all indigestible or slowly absorbed, short-chain carbohydrates would minimise stretching of the intestinal wall. This was proposed to reduce stimulation of the gut’s nervous system and provide the best chance of reducing symptom generation in people with IBS (see below). At the time, there was no collective term for indigestible or slowly absorbed, short-chain carbohydrates, so the term ‘FODMAP’ was created to improve understanding and facilitate communication of the concept.[1]

The low FODMAP diet was originally developed by a research team at Monash University in Melbourne, Australia.[22] The Monash team undertook the first research to investigate whether a low FODMAP diet improved symptom control in patients with IBS and established the mechanism by which the diet exerted its effect.[2][32] Monash University also established a rigorous food analysis program to measure the FODMAP content of a wide selection of Australian and international foods.[33][34][35] The FODMAP composition data generated by Monash University updated previous data that was based on limited literature, with guesses (sometimes wrong) made where there was little information.[36]

Role in non-celiac gluten sensitivity

FODMAPs that are present in gluten-containing grains have been identified as a possible cause of gastrointestinal symptoms in people with non-celiac gluten sensitivity, in place of,[37] or in addition to, gluten and other proteins in gluten-containing cereals, named amylasetrypsin inhibitors (ATIs).[14][13] The amount of fructans in these cereals is small. In rye they account for 3.6%–6.6% of dry matter, 0.7%–2.9% in wheat, and barley contains only trace amounts.[3] They are only minor sources of FODMAPs when eaten in the usual standard amounts in the daily diet.[13] Wheat and rye may comprise a major source of fructans when consumed in large amounts.[7]

In a 2018 double-blind, crossover research study on 59 persons on a gluten-free diet with challenges of gluten, fructans or placebo, intestinal symptoms (specifically bloating) were borderline significantly higher after challenge with fructans, in comparison with gluten proteins (P=0.049).[3][17] Although the differences between the three interventions was very small, the authors concluded that fructans are more likely to be the cause of gastrointestinal symptoms of non-celiac gluten sensitivity, rather than gluten.[3] In addition, fructans used in the study were extracted from chicory root, so it remains to be seen whether the wheat fructans produce the same effect.[17]

A 2018 review concluded that although fructan intolerance may play a role in non-celiac gluten sensitivity, it only explains some gastrointestinal symptoms, but not the extra-digestive symptoms that people with non-celiac gluten sensitivity may develop, such as neurological disorders, fibromyalgia, psychological disturbances, and dermatitis; and that FODMAPs cause digestive symptoms when the person is hypersensitive to luminal distension.[3]

A 2019 review concluded that wheat fructans can cause certain IBS-like symptoms, such as bloating, but they are not likely to cause immune activation nor extra-digestive symptoms since, in fact, many people with non-celiac gluten sensitivity report resolution of their symptoms after removing gluten-containing cereals while they continue to eat fruits and vegetables with high FODMAPs content in their diet.[17]

^ abcdefgVerbeke, K (February 2018). “Nonceliac Gluten Sensitivity: What Is the Culprit?”. Gastroenterology. 154 (3): 471–473. doi:10.1053/j.gastro.2018.01.013. PMID29337156. Although intolerance to fructans and other FODMAPs may contribute to NCGS, they may only explain gastrointestinal symptoms and not the extraintestinal symptoms observed in NCGS patients, such as neurologic dysfunction, psychological disturbances, fibromyalgia, and skin rash.15 Therefore, it is unlikely that they are the sole cause of NCGS.

^ abcdeStaudacher HM, Irving PM, Lomer MC, Whelan K (April 2014). “Mechanisms and efficacy of dietary FODMAP restriction in IBS”. Nature Reviews. Gastroenterology & Hepatology (Review). 11 (4): 256–66. doi:10.1038/nrgastro.2013.259. PMID24445613. An emerging body of research now demonstrates the efficacy of fermentable carbohydrate restriction in IBS. […] However, further work is urgently needed both to confirm clinical efficacy of fermentable carbohydrate restriction in a variety of clinical subgroups and to fully characterize the effect on the gut microbiota and the colonic environ¬ment. Whether the effect on luminal bifidobacteria is clinically relevant, preventable, or long lasting, needs to be investigated. The influence on nutrient intake, dietary diversity, which might also affect the gut microbiota, and quality of life also requires further exploration as does the possible economic effects due to reduced physician contact and need for medication. Although further work is required to confirm its place in IBS and functional bowel disorder clinical pathways, fermentable carbohydrate restriction is an important consideration for future national and international IBS guidelines.

^ abcdVolta U, De Giorgio R, Caio G, Uhde M, Manfredini R, Alaedini A (March 2019). “Nonceliac Wheat Sensitivity: An Immune-Mediated Condition with Systemic Manifestations”. Gastroenterol Clin North Am (Review). 48 (1): 165–182. doi:10.1016/j.gtc.2018.09.012. PMC6364564. PMID30711208. Furthermore, a role for the FODMAP (eg, fructans) component of wheat as the sole trigger for symptoms is somewhat doubtful, because many patients with NCWS report resolution of symptoms after the withdrawal of wheat and related cereals, while continuing to ingest vegetables and fruits with high FODMAP content in their diets.59 On the whole, it is conceivable that more than one culprit may be involved in symptoms of NCWS (as they are currently defined), including gluten, other wheat proteins, and FODMAPs.60–62

^ abcBarrett JS (March 2017). “How to institute the low-FODMAP diet”. Journal of Gastroenterology and Hepatology (Review). 32 Suppl 1: 8–10. doi:10.1111/jgh.13686. PMID28244669. Common symptoms of IBS are bloating, abdominal pain, excessive flatus, constipation, diarrhea, or alternating bowel habit. These symptoms, however, are also common in the presentation of coeliac disease, inflammatory bowel disease, defecatory disorders, and colon cancer. Confirming the diagnosis is crucial so that appropriate therapy can be undertaken. Unfortunately, even in these alternate diagnoses, a change in diet restricting FODMAPs may improve symptoms and mask the fact that the correct diagnosis has not been made. This is the case with coeliac disease where a low-FODMAP diet can concurrently reduce dietary gluten, improving symptoms, and also affecting coeliac diagnostic indices. Misdiagnosis of intestinal diseases can lead to secondary problems such as nutritional deficiencies, cancer risk, or even mortality in the case of colon cancer.